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Abstract:

A method for surface-modifying a sensor device is disclosed, which
includes the following steps: providing a sensor device, wherein a
surface of the sensor device has a metal film; forming a
surface-modification layer having a plurality of carboxyl groups on the
metal film of the sensor device by isopropyl alcohol plasma; and forming
a poly(acrylic acid) layer on the surface-modification layer, wherein the
acrylic acid of the poly(acrylic acid) layer is grafted to the carboxyl
of the surface-modification layer. A surface-modified sensor device is
also disclosed.

Claims:

1. A method for surface-modifying a sensor device comprising the
following steps: providing a sensor device, wherein a surface of the
sensor device has a metal film; forming a surface-modification layer
having a plurality of carboxyl groups on the metal film of the sensor
device by isopropyl alcohol plasma; and forming a poly(acrylic acid)
layer on the surface-modification layer, wherein the acrylic acid of the
poly(acrylic acid) layer is grafted to the carboxyl groups of the
surface-modification layer.

2. The method as claimed in claim 1, further comprising the following
step: forming a bio-molecule layer on the poly(acrylic acid) layer,
wherein bio-molecules of the bin-molecule layer are bonded to the
carboxyl groups of poly(acrylic acid) of the poly(acrylic acid) layer.

3. The method as claimed in claim 2, wherein the biomolecules are protein
A or serum albumin.

4. The method as claimed in claim 2, wherein the biomolecules of the
bio-molecule layer are bonded to the poly(acrylic acid) layer in the
presence of a coupling activator.

5. The method as claimed in claim 1, wherein the metal layer is a gold or
silver layer.

6. The method as claimed in claim 1, wherein the poly(acrylic acid) layer
grafted to the carboxyl groups of the surface-modification layer is
formed by the polymerization of acrylic acid under UV illumination.

7. A surface-modified sensor device, comprising: a sensor device, on
which a metal film is disposed; a surface-modification layer having a
plurality of carboxyl groups on the metal film of the sensor device,
wherein the surface-modification layer is formed by isopropyl alcohol
plasma; and a poly(acrylic acid) layer on the surface-modification layer,
wherein the acrylic acid of the poly(acrylic acid) layer is grafted to
the carboxyl groups of the surface-modification layer.

8. The surface-modified sensor device as claimed in claim 7, further
comprising: a bio-molecule layer located on the poly(acrylic acid) layer,
wherein bio-molecules of the bio-molecule layer are bonded to the
carboxyl groups of poly(acrylic acid) of the poly(acrylic acid) layer.

9. The surface-modified sensor device as claimed in claim 8, wherein the
biomolecules are protein A or serum albumin.

10. The surface-modified sensor device as claimed in claim 8, wherein the
biomolecules of the bio-molecule layer is bonded to the poly(acrylic
acid) layer in the presence of a coupling activator.

11. The surface-modified sensor device as claimed in claim 7, wherein the
metal layer is a gold or silver layer.

12. The surface-modified sensor device as claimed in claim 7, wherein the
poly(acrylic acid) layer grafted to the carboxyl groups of the
surface-modification layer is formed by the polymerization of acrylic
acid under UV illumination.

[0003] The present invention relates to a surface-modified sensor device
and a method for surface-modifying a sensor device and, more
particularly, to a surface-modified sensor device with increased density
of bonded molecules and uniformity and a method for surface-modifying a
sensor device.

[0004] 2. Description of Related Art

[0005] In recent years, the application of optical sensors has become a
major trend in biomolecule detection for medical diagnosis and film
thickness measurement. In the biomolecule detection, the biomolecules are
required to be immobilized on the sensor devices and then reacted with
the test sample to provide a signal variation for the determination of
the species and amount of the test sample.

[0006] If the biomolecules require to be immobilized on the metal coatings
of the optical sensors, the metal coatings need to be modified first. In
the conventional surface modification for the biomolecules, the optical
sensors are immersed in an 11-mercaptoundecanoic acid (MUA) solution. By
way of the immersion, it is expected that the lone pair of sulfur in MUA
will occupy an outer vacant orbital of a metal atom to form a stable
coordination bond therebetween. Accordingly, carboxyl groups (COOH) are
formed on the metal coatings to achieve the modification thereof.
Subsequently, the carboxyl groups of the surface modification layer are
bonded to biomolecules in the presence of a coupling activator,
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) N-hydroxysuccinimide
(NHS), to realize biomolecule immobilization.

[0007] Nevertheless, such chemical modification of immersion in MUA
involves considerable reaction time and causes the metal coatings to have
uneven surface hydrophilicity, leading to undesirable result of the
modification. Accordingly, the modification cannot achieve the
anticipated level and has drawbacks such as long waiting time, increased
experimental instability, and reduced uniformity.

[0008] Therefore, it is desirable to provide a method for
surface-modifying a sensor device to give the metal coating of the sensor
device uniform surface hydrophilicity so that the detection properties,
sensitivity, and so on of the sensor device can be improved to benefit
the accuracy of the of the biomolecule detection.

SUMMARY OF THE INVENTION

[0009] The object of the present invention is to provide a method for
surface-modifying a sensor device. The method can increase the number of
carboxyl groups and hydrophilicity of the surface of the sensor device,
thereby enhancing the immobilization of the biomolecules.

[0010] To achieve the object, one aspect of the present invention provides
a method for surface-modifying a sensor device including the following
steps: providing a sensor device, wherein a surface of the sensor device
has a metal film; forming a surface-modification layer having a plurality
of carboxyl groups on the metal film of the sensor device by isopropyl
alcohol plasma; and forming a poly(acrylic acid) layer on the
surface-modification layer, wherein the acrylic acid of the poly(acrylic
acid) layer is grafted to the carboxyl groups of the surface-modification
layer.

[0011] In the abovementioned method of the present invention, after the
treatment of isopropyl alcohol plasma, carboxyl groups (COOH) can be
formed on the metal film of the sensor device and subsequently grafted
with acrylic acid by polymerization so that a poly(acrylic acid) layer
can be formed on the sensor device. Meanwhile, the time for performance
of the plasma modification can be in a range from 1 to 30 minutes, or
from 5 to 15 minutes. During the performance of the plasma modification,
the strength of watts or pressure can be determined on the kind of the
plasma, the time of the performance, and so on.

[0012] Compared with a sensor device modified only with isopropyl alcohol
plasma, much more carboxylic groups, more uniform distribution of the
carboxylic groups, and better hydrophilicity are introduced in the sensor
device of the present invention treated with the combination of the
isopropyl alcohol plasma modification and the acrylic acid polymerization
so as to benefit subsequent immobilization of bio-molecules, leading to
improvement of sensitivity and detection properties of the sensor device.

[0013] In the abovementioned method for surface-modifying a sensor device,
the kind of the sensor device is not limited and it can be, for example,
an optical fiber sensor device. Also, the kind of the metal film on the
sensor device is not limited. However, the metal film can be a gold or
silver film in order to give the optical sensor device a preferable
reaction. In general, a gold film is used as the metal film. The
thickness of the film is not limited and is preferably in a range from 20
nm to 80 nm, for example 40±5 nm. The formation of the film is also
not limited and it can be any manner used by a person skilled in the art
of the present invention, for example electroplating or arranging metal
nanoballs to form a film.

[0014] Therefore, if a metal film on a sensing area of an optical fiber
sensor device is treated with the method of the present invention and
then bio-molecules are immobilized thereon, this device can be used to
detect a sample according to surface plasmon resonance (SPR).

[0015] The abovementioned method for surface-modifying a sensor device can
further include the following step: forming a bio-molecule layer on the
poly(acrylic acid) layer, wherein bio-molecules of the bio-molecule layer
are bonded to the carboxyl groups of poly(acrylic acid) of the
poly(acrylic acid) layer.

[0016] The aforesaid bio-molecules can be antibodies, antigens, enzymes,
parts of tissues, or single cells. For example, since protein A or serum
albumin is able to bind to the Fc region of an antibody, an antigen can
be specifically recognized by the antibody bonded to the protein A or
serum albumin (serving as the bio-molecules) immobilized on the thin
metal film. Hence, the optical sensors modified in the abovementioned
method can specifically detect the antigen recognized by the antibody
bonded to the protein A or serum albumin, and thus identify the antigen
and its concentration.

[0017] In the abovementioned method for surface-modifying a sensor device
of the present invention, the biomolecules of the bio-molecule layer are
bonded to the poly(acrylic acid) layer in the presence of a coupling
activator. The coupling activator can be selected from a group consisting
of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),
N-hydroxy-succinimide (NHS), and a combination thereof.

[0018] In the abovementioned method for surface-modifying a sensor device,
said poly(acrylic acid) grafted with the carboxyl groups can be formed by
the polymerization of acrylic acid under UV illumination. In other words,
under UV illumination, grafting polymerization of acrylic acid is carried
on to make poly(acrylic acid) be grafted the carboxyl groups of the
surface modification layer. Accordingly, more and uniform carboxyl groups
can be formed on the sensor device.

[0019] Another object of the present invention is to provide a
surface-modified sensor device to give better detection properties,
sensitivity etc. so as to promote the accuracy of the biomolecule
detection.

[0020] In order to achieve the object mentioned above, another aspect of
the present invention provides a surface-modified sensor device
including: a sensor device, on which a metal film is disposed; a
surface-modification layer having a plurality of carboxyl groups on the
metal film of the sensor device, wherein the surface-modification layer
is formed by isopropyl alcohol plasma; and a poly(acrylic acid) layer on
the surface-modification layer, wherein the acrylic acid of the
poly(acrylic acid) layer is grafted to the carboxyl groups of the
surface-modification layer.

[0021] The surface-modified sensor device of the present invention said
above can further include: a bio-molecule layer located on the
poly(acrylic acid) layer, wherein bio-molecules of the bio-molecule layer
are bonded to the carboxyl groups of poly(acrylic acid) of the
poly(acrylic acid) layer. Particularly, the biomolecules are not limited
and they can be protein A or serum albumin. Besides, the biomolecules of
the bio-molecule layer can be bonded to the poly(acrylic acid) layer in
the presence of a coupling activator.

[0022] In the surface-modified sensor device of the present invention, the
metal film can be a gold or silver film, and the poly(acrylic acid) layer
can be formed by the polymerization of acrylic acid under UV
illumination.

[0023] In conclusion, the present invention combines surface modification
of isopropyl alcohol plasma and grafting polymerization of acrylic acid
to promote the stability of the manufacturing and efficiently control the
density of the bonding molecules. In addition, the surface modification
formed by isopropyl alcohol plasma has considerable and evenly
distributing carboxyl groups and low porosity, and thus exhibits good
coverage and adherence to the metal film of the sensor device.
Furthermore, grafting polymerization of acrylic acid is carried on to
form a poly(acrylic acid) layer on the surface modification layer to
introduce more carboxyl groups uniformly distributing on the sensor
device. Therefore, the surface hydrophilicity of the sensor device is
significantly enhanced. Also, the increase in the number of the carboxyl
groups can benefit the subsequent immobilization of the biomolecules so
as to improve the detection properties and accuracy of the sensor device.

[0024] Other objects, advantages, and novel features of the invention will
become more apparent from the following detailed description when taken
in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIGS. 1A to 1D show a flowchart of the method for surface-modifying
a sensor device in Example 1 of the present invention;

[0026] FIG. 1E show a perspective view of a sensor device in Example 2 of
the present invention;

[0027] FIG. 2A is a FTIP (Fourier transform infrared spectroscopy)
spectrum of the sensor device of Comparative Example 1 in Test Example of
the present invention; and

[0028]FIG. 2B is a FTIP spectrum of the sensor device of Example 1 in
Test Example of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Because of the specific embodiments illustrating the practice of
the present invention, one skilled in the art can easily understand other
advantages and efficiency of the present invention through the content
disclosed therein. The present invention can also be practiced or applied
by other variant embodiments. Many other possible modifications and
variations of any detail in the present specification based on different
outlooks and applications can be made without departing from the spirit
of the invention.

[0030] The drawings of the embodiments in the present invention are all
simplified charts or views, and only reveal elements relative to the
present invention. The elements revealed in the drawings are not
necessarily aspects of the practice, and quantity and shape thereof are
optionally designed. Further, the design aspect of the elements can be
more complex.

Example 1

[0031] With reference to FIG. 1A to 1D, there is a flowchart of a method
for surface modifying a sensor device in the present invention.

[0032] First, as shown in FIG. 1A, a sensor device 20 is provided and it
has a metal film 21 disposed on a surface thereof. In the present
example, the sensor device 20 is an optical fiber sensor device such as a
side-polishing optical fiber sensor device, and its surface has a sensing
area. On the surface of the sensing area, a gold film is formed by the
method of depositing metal films such as sputtering and serves as the
metal film 21.

[0033] Subsequently, as shown in FIG. 1B, a surface modification layer 23
having a plurality of carboxyl groups is formed on the metal film 21 of
the sensor device 20 by isopropyl alcohol plasma. In the present example,
the isopropyl alcohol plasma is carried on in the following manner.
Isopropyl alcohol is used as material gas and introduced in to a vacuum
discharge tube. Discharging ionizes isopropyl alcohol and then various
chemical active species are produced. After complex chemical reactions,
products are deposited on the metal film 21 of the sensor device 20 to
form a surface modification layer 23 having a plurality of carboxyl
groups. Therefore, the metal film 21 of the sensor device 20 is modified
to obtain many carboxyl groups thereon. The surface modification layer 23
formed thereby has low thickness and porosity, and evenly covers the
surface of the metal film 21 of the sensor device 20.

[0034] Then, as shown in FIGS. 1C and 1D, acrylic acid is used as a
monomer and grafting polymerization thereof is performed under UV
illumination. Hence, acrylic acid monomers are grafted to the carboxyl
groups of the surface modification layer 23 and forms a poly(acrylic
acid) layer 24.

Example 2

[0035] First, as mentioned in Example 1, the surface of the sensor device
20 is modified to form the surface modification 23 and the poly(acrylic
acid) layer 24 on the metal film 21 of the sensor device 20.

[0036] Subsequently, as shown in FIG. 1E, the carboxyl groups of the
poly(acrylic acid) layer 24 is activated by a coupling activator. Plural
biomolecules 24 are provided and their amino groups are bonded to the
carboxyl groups of the poly(acrylic acid) layer 24 to form a biomolecule
layer. In the present invention,
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is used as the coupling
activator.

Comparative Example 1

[0037] In the manner similar to that mentioned in Example 1, the metal
film 21 of the sensor device 20 is surface-modified. However, surface
modification employs only isopropyl alcohol plasma.

[0039] According to the FTIP spectrums, the sensor device of Example 1
(surface-modified by isopropyl alcohol plasma and grafting polymerization
of acrylic acid) has more carboxyl groups and hydrophilic functional
groups such as hydroxyl groups than that of Comparative Example 1 (only
surface-modified by isopropyl alcohol plasma).

[0040] In conclusion, if a metal film is formed evenly by sputtering on
the surface of the sensor device, SPR response can occur thereon. When a
surface modification layer having carboxyl groups is formed on the metal
film by isopropyl alcohol plasma, and acrylic acid used as a monomer is
grafted to the carboxyl groups under UV illumination and then polymerized
to form a poly(acrylic acid) layer, the functional groups of the metal
film of the sensor device can be modified by the abovementioned mixture
of the chemical films of the present invention. The increase on the
number of the carboxyl groups on the surface can enhance the subsequent
immobilization of the biomolecules and also hydrophilicity of the surface
of the sensor device. Furthermore, since the immobilization of the
biomolecules is enhanced, the detection efficiency can be improved and
detection accuracy and reaction speed can both advanced.

[0041] Although the present invention has been explained in relation to
its preferred embodiment, it is to be understood that many other possible
modifications and variations can be made without departing from the scope
of the invention as hereinafter claimed.